Page:Popular Science Monthly Volume 53.djvu/27

thousand feet more, with the production of a narrow gorge having precipitous walls, not yet widened into a mature valley. Channels like that of the Colorado also occur crossing submarine plateaus.

Plate II.—Valley of the Rosseau, Dominica. A short, deep valley, heading in an amphitheater and dissecting a denuded plateau.

The short tributaries of these high plateau valleys may be likened to gigantic washouts. Such short, deep valleys commonly form at their heads amphitheaters, which may be a few miles in length, as is illustrated in Plate II. These are sometimes so precipitous